Tuning Question

[Little Fork Runner]

What will I have to do differently to my stock yamato 302 motor when I put an expansion chamber on. Will I have to re jet it or just adjust the carb??? Also will I have to change the timing from the stock setting???
Thanks

[Aussie Steve]

Shouldn't have to change timing or jets just fatten up mixer dial about 4-5 clicks , a well tuned pipe will suck you dry and stick your motor , I'm no expert maybe some one else can chime in

[Little Fork Runner]

Thanks for the replay. Thats the same thing that i just heard from someone else, so now i will know what to do when i finish making my pipe.
Thanks

[sam]

Turn the carb rich and run the boat. Check the spark plug color. If darker than Hershey Chocolate, run again a couple clicks leaner. Repeat until color lightens up or motor sticks. The best color is a light brownish tan. All tan is too lean ... probably be the color on the plug when the motor is stuck.

Then I'd recommend test running the boat with the pipe off. If the motor does not run noticably richer with the pipe off ... the pipe is not doing anything.

[Little Fork Runner]

Turn the carb rich and run the boat. Check the spark plug color. If darker than Hershey Chocolate, run again a couple clicks leaner. Repeat until color lightens up or motor sticks. The best color is a light brownish tan. All tan is too lean ... probably be the color on the plug when the motor is stuck.

Then I'd recommend test running the boat with the pipe off. If the motor does not run noticably richer with the pipe off ... the pipe is not doing anything.

so reading the plugs is the best way to see if it is tuned properly. what are you refering to when you say motor is stuck??? its too lean and the pistons aren't properly lubricated, so the motor ceases up cause i want to make sure that doen't happen. i have already had a bad experience with that on my snowmobile.
Thanks

[sam]

You can try tuning for the fastest speed, but if you don't watch the plugs ... you will probably be buying some pistons and muriatic acid.

[Little Fork Runner]

You can try tuning for the fastest speed, but if you don't watch the plugs ... you will probably be buying some pistons and muriatic acid.

haha thanks for letting me know, i will definatly check my plugs often to make sure that doesn't happen!!!

[Aussie Steve]

To True

You can try tuning for the fastest speed, but if you don't watch the plugs ... you will probably be buying some pistons and muriatic acid.

Yeah stuck mine twice last year now I carry pistons rings and acid with Qtips lol.

[Little Fork Runner]

Yeah stuck mine twice last year now I carry pistons rings and acid with Qtips lol.

how much does it cost on average to do a rebuild like that??? pistons, rings, gaskets, and what is the acid for???

[seanp3]

how much does it cost on average to do a rebuild like that??? pistons, rings, gaskets, and what is the acid for???

The acid is for cleaning the allum off the cyl wall from the stuck piston. Not sure what the current pricing is for pistons, rings and gaskets. However, they're pretty cheap for the Yamatos in comparison to other motors

[Little Fork Runner]

The acid is for cleaning the allum off the cyl wall from the stuck piston. Not sure what the current pricing is for pistons, rings and gaskets. However, they're pretty cheap for the Yamatos in comparison to other motors

Yea i figured that the acid was being used as some kind of cleaning component. does anyone know where i can find the 18mm spark plug reducer to 14mm. im just kind of wondering what a ballpark price would be because i cant find the 18mm plugs anywhere???

[ZUL8TR]

adapters

18 to 14 mm adapters are about $30 for the set. Several suppliers have them. Check links on this site.

[mercguy]

Yea i figured that the acid was being used as some kind of cleaning component. does anyone know where i can find the 18mm spark plug reducer to 14mm. im just kind of wondering what a ballpark price would be because i cant find the 18mm plugs anywhere???

don't buy the spark plug reducers.......just buy a 14mm head................much better in the long run


PS: quit listenig to Sam talking about "sticking" your motor, that is not going to happen with a slight misadjustment of the carb...........it will "stick" if overheated or improper oil/gas mix.....................if either of those happens, muratic acid ain't going fix the cylinder damage..........

[hydroid]

302 Refresh parts

Pistons: $75 ea
Rings: $15 ea
Head gasket: $8

[Little Fork Runner]

Pistons: $75 ea
Rings: $15 ea
Head gasket: $8

thanks for the prices, so on average around $200 to fix if you stick your motor!!!